Countless companies in the manufacturing and construction industries rely on overhead cranes to lift and transport materials. When installed and used properly, these systems make operations easier and safer. But, overhead crane accidents cause severe injuries and fatalities every year. Preventing these disasters requires workers to recognize certain hazards that occur during operation and follow safety procedures to avoid them.
There are multiple hazards that can arise regarding cranes in general. Many accidents involve large lift systems like tower cranes and mobile cranes. But hazards do exist with all types of cranes—including overhead cranes—and in all facets of crane operation. (Overhead cranes are defined by OSHA 1910.179(a)(8) as a crane with a movable bridge carrying a movable or fixed hoisting mechanism, and traveling on an overhead fixed runway structure.) Analysis of overhead crane accidents reveals three common safety hazards that every company using overhead lift systems should be aware of to keep their workers safe. It’s important to be familiar with these hazards and learn to recognize them in the workplace in order to avoid them. The three most common hazards involving overhead cranes include electrical hazards, overloading, and materials falling/slipping from overhead hoists. The following analysis of each hazard provides a description, potential risks, reasons why accidents occur, preventative measures to avoid them, and applicable OSHA requirements. One commonality that all three hazards share is the qualifications of crane operators. It is the responsibility of the crane owner and job supervisor to ensure that crane operators are competent and qualified to do the job. Click here to read more about training requirements and minimum competent personnel guidelines outlined by OSHA.
According to OSHA, nearly 50 percent of overhead crane accidents are the result of machinery coming into contact with a power source during operation. Power line contact is literally defined as the inadvertent contact of any metal part of a crane with a high-voltage power line. Power line contact most often occurs when the crane is moving materials nearby or under energized power lines and the hoist line or boom touches one of them. Usually, the person who is electrocuted is touching the crane when it comes into contact with the power line. But, the danger is not just limited to the operator. It extends to all personnel in the vicinity.
A single contact with power lines can result in multiple deaths and injuries. Each year nearly 200 people die from power line contact and about three times as many are seriously injured. Most victims are guiding the load at the time of contact, but risks extend to everyone present at a job site.
Power line contacts most often occur because safety planning isn’t considered and preventative measures haven’t been taken to avoid hazards. Planning is one of the biggest accident deterrents available. To start, it’s important to establish who is in charge of prejob safety planning before any cranes arrive at a worksite. Furthermore, cranes should be kept away from unsafe working areas; OSHA and ANSI both outline safe distances operators must maintain from a power source when working at a job site. Areas that are considered hazardous are referred to as danger zones, and crane operators should be clearly notified of all potential danger zones. The area within a 10-foot radius of a power line is considered an unsafe work area—or danger zone—and it must be clearly marked on the ground by insulated barriers, fences, tape, etc. This will help create visual clues for workers to ensure that the crane is always positioned so that the boom and hoist line can’t intrude in the danger zone.
OSHA also regulates that overhead crane operators use precautions when working near power lines—even outside of the 10-foot radius. This means, operators should consider all power lines as energized until the electric company tells him or her otherwise. Operators should also maintain a safe speed when operating near power lines. Crane booms or truck-mounted trolleys using an electrical remote control system for loading and unloading can also be very dangerous. If the boom contacts a power line, the operator holding the control box is usually electrocuted instantly. This type of equipment should never be used near power lines. A non-conductive, pneumatic or radio remote control system is a much safer choice when working near power lines.
Overall, it’s important for operators and workers to receive the appropriate training to avoid danger zones where electrocution can occur. Operators should have workers observing nearby to assist them whenever it is difficult to visually maintain the necessary clearance. Be sure that any ladders, tools, and systems are non-conductive, and ask the electric company to de-energize and ground power lines or install insulation whenever people are working near them.
- 29 CFR 1910.333(c)(3)—Selection and use of work practices—Working on or near exposed energized parts—Overhead lines
- 29 CFR 1926.550(a)(15)—Cranes and derricks—General requirements—Electrical distribution and transmission lines
According to OSHA, 80 percent of all crane upsets and structural failures can be attributed to exceeding the crane’s operational capacity. When a crane is overloaded, it is subject to structural stresses that may cause irreversible damage. Swinging or sudden dropping of the load, using defective components, hoisting a load beyond capacity, dragging a load and side-loading a boom can all cause overloading.
OSHA estimates that one crane upset occurs for every 10,000 hours of crane use. Nearly 80 percent of these upsets can be attributed to predictable human error when the operator inadvertently exceeds the crane’s lifting capacity. Overloading most often occurs when poorly trained personnel are allowed to operate cranes. Oftentimes, operators mistakenly believe they are able to rely on their instinct or experience to determine whether a load is too heavy. It’s crucial that any crane operator know the weight of a load and the capacity of the crane. Using technologies such as load-measuring systems for training and planning can greatly reduce the hazard of overloading and operator incompetency.
OSHA requires workers to provide formal training for all crane operators, but operator certification is only required for operators using equipment with a maximum manufacturer-rated capacity of 2,000 pounds or less. Employees who are not qualified are only permitted to operate equipment as operators-in-training with a certified trainer. Formal training should ensure a working knowledge of crane load charts, and on-the-job training is a great preventative measure if the trainer is qualified.
Overall, most crane safety programs outline competent personnel requirements, and it’s a good idea to become familiar with them. Cranes have become more sophisticated, with the ability to lift heavier loads further and faster than ever before. Today’s operator must be well trained and have a clear understanding of load dynamics, lifting capacities at various configurations, and the conditions under which such lifting capacities are valid.
- 29 CFR 1910.179(g)(5)(iv)—Overhead and Gantry Cranes—Switches
- 29 CFR 1910.179(n)(4)(I)—Overhead and Gantry Cranes—Handling the load—Hoist limit switch
- 29 CFR 1910.179(a)(50)—Overhead and Gantry Cranes—Rated Load
- 29 CFR 1910.179(b)(8)—Overhead and Gantry Cranes—Designated Personnel
- 29 CFR 1910.179(a)(35)—Overhead and Gantry Cranes—Designated Employee
- 29 CFR 1926.550(g)(3)(ii)(C)—Cranes and Derricks—Instruments and Components
- 29 CFR 1926.21(b)—Safety Training and Education
Falling materials is a major concern at any work place or job site using overhead cranes. Visual impairment, two-blocking, slipping, mechanical failure, or operator incompetency can all result in serious injuries or fatalities. If materials are not properly secured, for instance, the load can slip and land on workers in the vicinity or cause major damage to property. For larger or mobile cranes, undesired movement of material can pinch or crush workers involved in the rigging process.
Statistics show that nearly 20 people died in 2012 as a result of accidents with overhead hoists. That’s because the loads being lifted by overhead hoists tend to be fairly heavy and cause serious damage if dropped. Slings and attachments that aren’t secured properly can be a major safety hazard, and when objects begin to slip, they will eventually crash to the floor below.
One way to reduce the risk of falling materials is to perform regular maintenance of hoists. Load testing maintenance ensures that you know how many pounds the hoist can handle, and it helps to maintain good working condition. Maintenance should always be treated seriously when it comes to heavy machinery. If a moving part on an overhead crane wears out or breaks the hoist, it can cause serious damage. Performing regular maintenance ensures the hoist and overhead crane remain in good working order and that all operations run smoothly.
Aside from maintenance, improper securing of the load or the slings that carry the load is one of the leading causes of accidents with overhead hoists and cranes. If the load or sling holding the load isn’t properly secured, the objects can slip out, tip, and eventually crash to the ground below. Mechanical failure can also cause machinery to malfunction unexpectedly and drop a heavy load. To reduce the risk, OSHA mandates that operators make daily crane inspections. When mechanical problems do arise, operators should use the lockout/tagout procedure to prevent accidental startup or movement of the crane until the problem has been repaired.
Employees working around overhead cranes should always wear proper head, foot, hand, and eye protection. The crane operator and any workers below should also be aware of his/her surroundings and never walk under a lift. A crane operator must always lower a load to the ground before leaving the lift or during idle times. When moving items, he or she should never raise the load higher than required for clearance.
When operating a hoist, properly trained employees in the vicinity should understand that they are working in a dangerous area. Installing “Hoist Danger” signs around the work area will help to alert employees that a hoist is operating over their heads. Workers should be trained to stay clear of the hoist, and they should never walk beneath loads suspended in the air. Likewise, suspended loads should never be moved over employees and personnel should never be lifted or transported on a hoist.
Careful operation of the hoist is another important safety factor to consider whenever overhead cranes are used. The person responsible for managing the hoist should be well trained and qualified. Moving the crane too quickly and jerking the hoist when it’s bearing a heavy load can be hazardous to the crane operator and workers nearby. Changing or reversing direction should be done slowly and carefully. Reversing direction can cause heavy loads to spill, and swinging the load is very risky. Operators and controllers must maintain 100 percent focus on the task at hand to avoid potentially dangerous situations.
- 29 CFR 1926.550(d)(3)—Cranes and Derricks—Overhead and Gantry Cranes
- 29 CFR 1910.179—Overhead and Gantry Cranes—Holding Brakes and Control Braking
- 29 CFR 1910.179(e)(6)(i)—Exposed Moving Parts
- 29 CFR 1910.179(f)(1)(ii) —Overspeeding
- 29 CFR 1910.179(b)(8)—Overhead and Gantry Cranes—Designated Personnel
- 29 CFR 1910.179(b)(6)—Overhead and Gantry Cranes—Clearance from Obstruction
- 29 CFR 1910.179(a)(42)—Overhead and Gantry Cranes—Hoists
Source: KRISTINA HARMAN, TECHNICAL WRITER | SPANCO.COM
OSHA 29 CFR 1926 and 29 CFR 1910